played this some more last night and i feel compelled to defend a couple of the decisions i've seen people questioning. the retry system, for me, isn't artificially extending the length of the game so much as it is protecting the tension. a couple of the enemy encounters happen right after an extra retry pickup. if i terribly screw one of those encounters up, i just hit 'retry last checkpoint', make sure i grab the extra retry again and repeat the encounter until i get through using a bare minimum of consumables (bullets, health, pitons, etc).
however, when i'm deep into a chapter, and an encounter happens, the tension is palpable. i much prefer the tension of encounters that happen far removed from a bonus checkpoint collectable.
in practice, i haven't really been pushed far back into the game because of the checkpoint system, but i have enjoyed the increased tension it brings. i feel there are enough retries to allow you to make consistant progress, but i know that i would hit 'retry' way more often if there was no penatly for doing so, and resources wouldn't feel nearly the same as they do.
take a locked area that has a padlock you need to shoot off... if you could just shoot the padlock off, and then hit retry to get your bullet back if the supplies inside weren't what you wanted, that would kill that decision.
so, the save system is for me, rather inspired... and the game wouldn't be nearly as good without it.
the other area i think needs defending is the combat. it is not, as some have said here, trial and error. yes, the first few times you face combat in this game, you won't know what to do, but that's more because you are still learning how it works. i get through most combat situations first try by paying attention.
you can gauge the agressiveness of the enemies based on what they say. you can see what weapons they have. if they rush you, it is generally quite easy to pick out the 'leader' that you need to kill in order to stave off the rush, and then you have time to assess the environment. if the enemies don't rush you, it's even easier.
I Am Alive is great, because it makes you plan out your actions. if you rush into the combat without thinking, that's how you get screwed up. if you dive into a dust cloud, or an extended climbing section without thinking, that's how you end up in a bad spot.
there are certainly things which are flaws. the graphics are certainly below average for example. stability issues (two hard locks for me in the second level... thankfully none since, but still) are always unforgiveable to me. climbing controls do seem a little loose at times, and often my character will climb to the left or right when i'm trying to make him climb down, and it's not an issue i've experienced in the recent PoP, Tomb Raider or Uncharted games.
but the retry system really feeds into the atmosphere of this game, and the combat is not trial and error in the slightest. it's just very different and it takes a few encounters to get the hang of.